Field of the Invention
The present invention relates to a power supply apparatus and an image forming apparatus that have power-saving mode.
Description of the Related Art
With the recent miniaturization trend in electronic equipment, there is an increasing need to miniaturize switching power supplies used in electronic equipment. In conventional power supply apparatuses, an electrolytic capacitor with a large capacitance and a high breakdown voltage is generally used for smoothing an AC voltage input from a commercial power supply into a DC voltage. Unfortunately, electrolytic capacitors have a problem of difficulty in miniaturization and profile reduction. In this regard, Japanese Patent Application Laid-Open No. 2012-29363 proposes a technique of miniaturizing a power supply apparatus by eliminating a smoothing capacitor.
However, for such power supply apparatuses without a primary-side smoothing capacitor as in Japanese Patent Application Laid-Open No. 2012-29363, and even for power supply apparatuses with a small-capacitance capacitor, there has been a desire to realize high power-supply efficiency even under light load by minimizing loss caused by changes in input voltage, along with a desire for miniaturization.